again, from W3:


Main Entry: col·lu·vi·um
Function: noun
Inflected Form(s): plural collu·via \-v\; or colluvi·ums \-mz\
Etymology: Medieval Latin, alteration of Latin colluvies
: a heterogeneous mass of rock detritus or soil material emplaced
primarily by gravitational processes on or at the foot of slopes; also :
alluvium emplaced at the foot of slopes by creek and slope wash